1. Field
The present invention relates to a wheel support bearing assembly for rotatably supporting a vehicle wheel such as used in, for example, an automotive vehicle and a method of manufacturing such wheel support bearing assembly.
2. Description of the Related Art
The wheel support bearing assembly for the support of a vehicle drive wheel of a structure shown in FIG. 18 has hitherto been suggested. See, for example, the Japanese Laid-open Patent Publication No. 09-164803. This known wheel support bearing assembly includes double rows of ball-shaped rolling elements 25 operatively interposed between raceway surfaces 23 defined in an outer member 21 and raceway surfaces 24 defined in an inner member 22, respectively. The inner member 22 referred to above is comprised of a hub axle 29, having an outer periphery formed with a radially outwardly extending hub flange 29a for the support of the vehicle wheel, and an inner race segment 30 mounted externally on a portion of the outer periphery of the hub axle 29 on an inboard side. The hub axle 29 has an axial bore 31 defined therein, into which a stem portion 33a of an outer race 33 of a constant velocity universal joint is inserted and then splined to the hub axle 29. With the step portion 33a splined to the hub axle 29 in this manner, an annular shoulder 33b of the constant velocity universal joint outer race 33 is urged against an inboard end face 30a of the inner race segment 30. When in this condition, a nut 34 is threadingly mounted on a free end of the stem portion 33a, the inner member 22 can be axially clamped between the constant velocity universal joint outer race 33 and the nut 34.
As shown in FIG. 19 showing a portion of FIG. 18 on an enlarged scale, in this suggested example, the inner race segment 30 is externally mounted on a radially inwardly depressed inner race mount 35, defined in an outer periphery of an inboard end portion of the hub axle 29. An inboard inner peripheral edge portion of the inner race segment 30, that is delimited between an annular inboard end face thereof and an inner peripheral surface thereof, is depleted axially inwardly of the inner race segment 30 to define a stepped area 36, so that when the inboard end portion of the hub axle 29 is deformed by a orbital forging to have a radially outwardly expanded diameter, the plastically deformed portion 29b can be crimped in position within the stepped area 36 in the inner race segment 30. By so doing, any possible detachment of the inner race segment 30 by the effect of an external force occurring during assemblage thereof into an automotive vehicle can be avoided.
It has however been found that the wheel support bearing assembly disclosed in the above mentioned patent document has the following problems:
(1) Since the plastically deformed portion 29b in the hub axle 29 is large in size, the stepped area 36 formed in the inboard end portion of the inner race segment 30 must have a large radial step (of a size having a radial difference of, for example, about 5 to 7 mm). If the size of the stepped area 36 is so large as described above, the surface area of the inboard end face 30a of the inner race segment 30 decreases correspondingly, resulting in an increase of the contact pressure between it and the shoulder 33b of the constant velocity universal joint outer race 33. For this reason, the known wheel support bearing assembly of the structure discussed above, when used in an actual automotive vehicle, tend to involve a cause of frictional wear and/or abnormal noises.
(2) If an attempt is made to accommodate the plastically deformed portion 29b in the hub axle 29 at a location axially inwardly of the inboard end of the inner race segment 30, the stepped area 36 in the inner race segment 30 must have an increased axial length (for example, about 7 to 8 mm). The use of the stepped area 36 in the inner race segment of the increased axial length may result in a tendency of the inner race stepped area 36 to assume a position on a linear line defining the angle of contact of the rolling elements and, therefore, there is the possibility that the lifetime will be reduced as a result of a considerable deformation of the inner race segment under the influence of a load imposed during the operation. The use of the inner race stepped area 36 of the increased axial length may also result in a reduction of the length (surface area), over which the inner race segment 30 is engaged on the hub axle 29, by a quantity corresponding to that reduced and, accordingly, the lifetime of the wheel support bearing assembly may be reduced as a result of occurrence of a creepage in the inner race segment. Although those problems can be resolved if the axial length of the inner race segment is increased, the increase of the axial length of the inner race segment may result in a requirement to increase an extra space in the axial direction.
(3) In addition, since the plastically deformed portion 29b in the hub axle 29 is large in size, a crimping punch may interfere with the inner race segment 30 during the orbital forging to such an extent as to result in a difficulty in processing.